Transmission-control system



July 24, 1928. 1,678,128

K. O. THORP TRANSMISSION CONTROL SYSTEM Filed Dec. 5, 1925 hvmfar: Ker/m 4 7/207,

Patented July 24, 1928.

UNITED STATES KERMIT 0. THORP, OF RIVER EDGE, NEW

COMPANY, INCORPORATED, OF NEW Y0 JERSEY, ASSIGNOR 'I'O WESTERN ELECTRIC RK, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION -CON TROL SYSTEM.

Application filed December 3, 1925. Serial No. 72,924.

This invention relates to transmission control systems and more particularly to a signal receiving system including a gain control for maintaining the volume of the reproduced speech signal at a uniform level.

Incarrier signaling systems in WlllCh call ringing currents are transmitted 1n the form of an interrupted continuous wave, 1t 1s desirable that the transmission level of this wave be sufliciently high to operate the desired selector and ringing device whereas the amplitude of the wave carrying speech s gnals must be such that the reproduced s1gnals are not. excessively loud. Consequently a gain control apparatus inserted in the clrcuit for the purpose of reducing the volume of speech signals to a predetermined maximum value should not operate to reduce the strength of the call ringing current An object of this invention is to l1m1t the volume of reproduced speech signals in a carrier signaling system to a uniform level, but to allow the call ringing signal to exceed this value.

The above object, and others which will be apparent as the nature of the inventlon 1s dlsclosed, are accomplished in a signaling system of the above mentioned character by incorporating a gain control with the receiving system to maintaln the reproduced speech at a uniform level, and includmg means for rendering the gain control moperative when ringing currents are being received.

Although the novel features whlch are believed to be characteristic of this invention will be pointed out with particular ty n the claims appended hereto, the invention itself, its objects and advantages, the mode of 1ts operation and the manner of its organ zation will be better understood by referring to the following description taken in connection with the accompanying drawing forming a part thereof, in which;

The figure is a diagrammatic representation of a signaling system constructed in accordance with this invention.

In the system disclosed in the drawing, line 1 represents the transmission line of a wire carrier system, or the antenna input circuit of a radio receiving system, over which signaling currents and call ringing currents are to be received. Line 1 is coupled by means of transformer 2 to the input circuit of space discharge amplifier 3 which is adapted to raise the potential of the impressed Waves to the required value and also to control the level of the potentials impressed upon the apparatus connectedthereto. The potential impressed upon the input circuit of space discharge amplifier 3 is controlled by means of a potentiometer comprising resistance 4 and associated rotatable contact arms 5 and 20.

In the position shown, herein called the normal position, a direct connection is made by means of contact arm 20 between line 22 and line 23, connected respectively to the secondary of transformer 2 and to the oathode of space discharge device 3. When contact arms 5 and 20 have revolved from the normal position in a counter-clockwise direction to any position other than that shown, line 22 will be connected to the lower end of resistance 4 through line 25, connectmg wire 24 and contact arm 20. At the same time the cathode of space discharge device will be connected by means of arm 5 and line 23 to any one of the series of taps on resistance 4, the inclusion of all the resistance as by means of the end tap corresponding to the second largest impressed potential.

Amplifier 3 is coupled to detector 29 by transformer 30. Receiving apparatus R and space discharge rectifier 7 are connected in parallel to the output circuit of detector 29. Receiver R is coupled to detector 29 by means of transformer 11 and rectifier 7 is coupled to the same circuit through transformer 6 having its primary connected in series with by-pass condenser 31 which offers low impedanceto high frequency currents and high impedance to voice frequency currents. The circuit including transformer 11 offers a low impedance path for voice frequency currents and a high impedance path for high frequency currents.

Receiver B may comprise one or more audio frequency amplifiers of any type capable of operating in conjunction with detec tor 29. However, as the particular apparatus incorporated in this receiver forms no part of this invention, it is shown here in diagrammatic form only. The incoming energy is demodulated and made available in suitable signal indicating means shown as telephone receiver 26.

The call signaling current, which in this system comprises an interrupted continuous wave, actuates relay 9, connected in the anode circuit of rectifier 7 in series with space current source 8, causing armature 13 to operate in accordance with the received impulses. Armature 13 is used to actuate a selector ringing system, shown as rectangle 12, by means of which the desired line is selected and the ringing current transmitted to the selected apparatus. The particular type of stepping mechanism and call ringing system employed forms no part of this invention and hence is not described in detail in connection herewith.

hen the desired line has been selected and the signal completed, receiver 26 is removed from its hook. This closes contacts 27 and completes the circuit from battery 28 to relay 14. Armature 16 of relay 14 is adapted to open the shunt circuit around relay 10 and thereby insert relay 10 in series with space current source 8 and relay 9 in the anode circuit of rectifier 7. Armature 17 of relay 1 1 is connected so as to open the circuit between rotating switch 19 and relay 18.

Relay 10 is adjusted to operate to close contact 21 thereby completing the circuit through self-interrupting stepping relay 18 whenever the received signal is of amplitude greater than a predetermined value. Relay 18 operates to rotate contacts 5, 19 and 20 in a counter-clockwise direction until a sufficient amount of resistance is inserted in the input circuit of space discharge device 3 to reduce the intensity of the signal in receiver 26 to the predetermined value or to an intensity lower than this value by an amount suflicient to allow relay 1O torelease. \Vhen this value has been reached the space current of tube 7 and consequently the current flowing in relay 10 is reduced sufliciently to allow contact 21 to open and break the circuit through relay 18. Contactors 5, 19 and 20 will then remain in the position which they have assumed. WVhen the call is completed and receiver 26 is replaced on its hook, relay 14 is deenergized and armatures 16 and 17 released. Armature 16 short circuits relay 10 and armature 17 completes the circuit between relay 18 and ground through contactor 19. Relay 18 then operates to step the movable contact arms farther in a counter-clockwise direction until they have assumed positions 180 from their original positions which correspond to those shown. The circuit is then broken by contactor 19 and the line is in a condition to receive the next call.

By means of a system constructed in accordance with this invention, a large call ringing current is allowed to be transmitted through the signal receiving apparatus to actuate the selector and ringing mechanism whereas the amplitude of the signaling current is limited by the gain control device to a predetermined maximum value.

'Althou h this invention has been shown and described with reference to a particular system operating in a particular manner, it is not to be limited thereto, but only in accordance with the scope of the following claims.

What is claimed is:

l. A transmission control system comprising a transmission line, means for transmit-- ting signal current and call signaling current over said line, means for limiting the volume of a reproduced signal and means for rendering said volume control means inoperative during the transmission of a call signaling current. 2. A transmission control system comprismg a transmission line, means for receiving and demodulating a modulated carrier wave transmitted over said line, means for controlling the amplitude of the demodulated wave, means for receiving call signaling current transmitted over said line, and means for rendering inoperative said volume control means while said call signaling current is being received.

3. In a transmission control system, a transmission line, a space discharge amplifier connected to said line, a potentiometer included in the input circuit of said amplifier for varying the potential impressed thereon in response to a received wave, call r nging apparatus, means for actuating said rlnging apparatus in response to an un modulated carrier wave received over said line, and means for rendering said potentiometer inoperative when said call ringing current is being received.

4. A transmission control system comprising a transmission line, a space discharge amplifier, means for receiving and impressing upon said amplifier a modulated carrier wave from said line, a potentiometer for controlling the potential impressed upon the input circuit of said amplifier in response to said received wave, stepping mechanism for controlling the position of said potentiometer, means for demodulating said modulated carrier wave to produce an audible signal therefrom, a space discharge rectifier, means for impressing a portion of said received wave thereon, means for controlling the position of said potentiometer in response to the current value in the anode circuit of said space discharge rectifier, call ringing selector apparatus, means for actuating said apparatus in response to an unmodulated carrier wave received over said line, and means for rendering inoperative said potentiometer control means while said unmodulated carrier wave is being received.

In witness whereof, I hereunto subscribe my name this 1st day of December, A. D. 1925.

KERMIT O. THORP. 

